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SubjectRe: [patch] genapic: optimize & fix APIC mode setup

* Andi Kleen <ak@suse.de> wrote:

> On Saturday 11 November 2006 16:14, Ingo Molnar wrote:
> > From: Ingo Molnar <mingo@elte.hu>
> >
> > this patch fixes a couple of inconsistencies/problems i found while
> > reviewing the x86_64 genapic code (when i was chasing mysterious eth0
> > timeouts that would only trigger if CPU_HOTPLUG is enabled):
> >
> > - AMD systems defaulted to the slower flat-physical mode instead
> > of the flat-logical mode. The only restriction on AMD systems
> > is that they should not use clustered APIC mode.
>
> This will open a race on CPU hotunplug unfortunately (common for multi
> core suspend)

Note that i386 still defaults to logical flat mode, so whatever hotplug
CPU races there are, they need to be fixed! Given how rare CPU hotplug
systems are i have no problem with having these races in the kernel for
a while until it's fixed.

Also, distro kernels enable CPU_HOTPLUG frequently. It is just ugly
beyond recognition to switch the programming of the IRQ hardware on
non-hotplug hardware just because a mostly-software feature (hotplug) is
enabled ...

if hotplug breaks suspend then fix it, dont hack it around (on one
platform) by slowing down the system [and causing other problems] ...

Ingo
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